A polymer battery, which is also called a lithium secondary battery, uses a polyelectrolyte, generates current by the migration of lithium ions and has positive and negative electrodes formed of active polymers.
The lithium secondary battery comprises a lithium battery module having a positive electrode collector (aluminum or nickel), a positive electrode active substance layer (metal oxide, carbon black, a metal sulfide, an electrolytic solution or a polymer for forming a positive electrode, such as polyacrylonitrile), an electrolytic layer (a carbonate electrolytic solution of propylene carbonate, ethylene carbonate, dimethyl carbonate or ethylene methyl carbonate, an inorganic solid electrolyte of a lithium salt or a gelled electrolyte), a negative electrode active layer (lithium, an alloy, carbon, an electrolytic solution or a polymer, such as polyacrylonitrile) and a negative electrode collector (copper, nickel, a stainless steel), and a package containing the lithium battery module therein.
The polymer battery is used as a power supply for personal computers, portable terminal devices (portable telephone sets and PDSs), video cameras, electric vehicles, energy storage batteries, robots, artificial satellites and the like.
The package of the polymer battery is a cylindrical or parallelepipedic metal can formed by pressing a metal sheet or a pouch formed by processing a laminated sheet consisting of a base layer, an aluminum layer and a sealant layer.
Such known packages for polymer batteries have the following problems. The meal can has rigid walls and hence the shape of the lithium battery module is dependent on that of the metal can. Since the hardware is designed so as to conform to the shape of the battery, the dimensions of the hardware are dependent on the shape of the battery, which reduces the degree of freedom of designing the shape of the hardware.
A pouch formed by heat-sealing two laminated sheets to contain a polymer battery module therein and an embossed package formed in the shape of a vessel by subjecting the laminated sheet to an embossing process to contain a polymer battery therein have been developed. The embossed package, as compared with the pouch, is a compact package. Satisfactory moistureproof property, strength including piecing resistance and insulating property are essential to polymer battery packages. Satisfactory formability is an additional important property of a laminated sheet for forming the embossed package.
More specifically, a packaging laminated sheet having a nylon layer, an adhesive layer, an aluminum layer, an adhesive layer and a cast polypropylene (PP) resin layer is an example of a polymer battery module packaging sheet for forming embossed packages. Even if the packaging laminated sheet is fabricated by a dry lamination process that makes the adhesive layers bond the adjacent layers with stable, high adhesive strength, sometimes, the packaging laminated sheet is delaminated and the nylon layer and the aluminum layer are separated when the packaging laminated sheet is subjected to an embossing process or when a package formed from the packaging laminated sheet is subjected to a heat-sealing process to heat-seal a peripheral part thereof after putting a polymer battery module in the package. Sometimes, the packaging laminated sheet is delaminated by hydrogen fluoride produced by the interaction of the electrolyte of the polymer battery module and moisture and the aluminum layer and the cast PP layer are separated.